The present invention relates to a sensor, and more precisely relates to a sensor, which is capable of detecting displacement length on the basis of mutual displacement length of coils.
Many types of sensors have been known. The applicant of the present invention also invented a displacement sensor. The displacement sensor was disclosed in U.S. Pat. No. 5,046,702. The displacement sensor has a coil, a diaphragm and a magnetizable body, which is fixed to the diaphragm and is capable of moving close to and away from the coil. When the magnetizable body moves close to and away from the coil with the movement of the diaphragm, reactance of the coil changes, so that displacement length of the diaphragm can be known by detecting the change of reactance thereof.
However, the conventional sensor has the following disadvantages.
Firstly, while the magnetizable body moves to the coil from outside, the reactance of the coil changes suddenly; on the other hand, while the magnetizable body goes into the coil, the reactance thereof changes gradually. Therefore, a practical sensing range, in which the displacement length of the magnetizable body can be practically detected, is limited to a range until the magnetizable body reached the coil. In other words, the displacement sensor has a small sensing range.
Secondly, a processor, which is capable of processing large amount of data, is required so as to convert the change of the reactance to the displacement length of the diaphragm because the reactance changes curvedly.